The invention relates to a heterojunction semiconductor device. The term heterojunction semiconductor device is understood to mean a device having a substrate on which have been formed layers of different compositions, usually by epitaxy. Such devices are well known in the art and the substrates are generally formed from the alloy GaAs (gallium arsenide) or InP (indium phosphide), whilst the active layers, i.e. those which directly contribute to the operation of the device are generally formed by ternary or quaternary mixtures comprising incorporated elements (doping agents).
This is the case in particular with electroluminescent diodes, photodetecting diodes and field effect transistors of the MESFET type (metal semiconductor field effect transistor of the Schottky type) comprising active zones which are the seat of light emission and the absorption of photons and where the conductive channel is formed in the case of MESFET.
In the case of electroluminescent diodes, for example of the laser type the active zone must be surrounded by two layers having a forbidden band width greater than that of the active zone.
Generally liquid phase epitaxy is used for producing such structures. However, liquid phase epitaxy is performed at temperatures of 500.degree. to 1000.degree. C. Consequently although the adaptation of the crystalline meshes conveniently takes place at the epitaxial temperature, this is not always the case at the operating temperature, because the thermal expansion coefficients are not always the same in different materials, which leads to disadvantages, particularly in the case of thermal shocks.